A liquid-crystal display device as one example of display devices is used in various fields. A liquid crystal panel of the liquid-crystal display device is roughly classified into a TN (Twisted Nematic) type, a VA (Vertical Alignment) type and an IPS (In-Plane Switching) type.
When a voltage is off, a liquid crystal panel of a TN type transmits light, with liquid crystal molecules being oriented in a direction parallel to a display surface. By gradually increasing a voltage, the liquid crystal molecules are allowed to gradually stand up toward being along a normal direction of the display surface, a light transmittance gradually decreases. When a voltage is off, a liquid crystal pane of a VA type blocks light, with liquid crystal molecules being oriented along a normal direction of a display surface. By gradually increasing a voltage, the liquid crystal molecules are gradually inclined toward being along the display surface, a light transmittance gradually increases. A liquid crystal panel of an IPS type adjusts a light transmittance by rotating liquid crystal molecules oriented along a display surface in accordance with application of voltage.
In a liquid crystal panel, it is generally important to control an amount and/or range of light that travels toward a front side, in order to suitably ensure a brightness, a contrast ratio and color reproducibility in a front view. On the other hand, to control light which travels in a direction inclined to a normal direction of a liquid panel is relatively complicated. Thus, in order to ensure a wide viewing angle and/or to sufficiently control a brightness, dispersions of a contrast ratio and color reproducibility in the viewing angle, a structure of the liquid panel may be complicated to undesirably increase cost. In order to deal with such a problem, Patent Documents 1 to 6, for example, respectively disclose an optical member provided on a display surface of a liquid crystal panel in order to widen a viewing angle due to a diffusion effect or the like. Such a member can simply improve a viewing angle.
Patent Document 1: JPH7-43704A
Patent Document 2: JP3272833B
Patent Document 3: JP3621959B
Patent Document 4: JP2016-126350A
Patent Document 5: JP2012-145944A
Patent Document 6: JP2011-118393A